Communication network



June 22, 1965 R. F. WHITE COMMUNICATION NETWORK 2 Sheets-Sheet l Filed July 19. 1960 June 22, 1965 R. F. wl-uTE COMMUNICATION NETWORK 2 Sheets-Sheet 2 lllllll'l brrr www Y km.

Filed July 19, 1960 United States Patent() 3,l9t`i,959 CBJHMUNHCATEN NETWRK Robert F. White, New York, NSY., assigner to Tele- Sessiens, lne., New York, NY., a corporation of New York Fiied .inly i9, 19nd, Ser. No. 43,335 S Claims. (Cl. 179-1) The present invention relates to improved communication systems in general, and it relates more particularly to improved communication systems for networking closed-circuit programs and broadcast programs which originate at a plurality of widely separated stations, and which alternately or simultaneously transmit While continuing to receive during the program, without the operation of switches or other controls and without prearrangement of the transmitting or receiving Sequence.

The systems heretofore employed and proposed for effecting simultaneous intercommunication among a plurality of remotely spaced stations or points possess nu- H merous drawbacks and disadvantages and at their best leave much to be desired. While their performance at relatively short distances is somewhat satisfactory, where the stations are widely separated diiiiculties are introduced which so adversely affect the performance of these systems as to greatly limit their use. In many of these multistation network systems it is necessary that signals are transmitted from the various stations in accordance with a predetermined sequence and that the switching operations be accordingly programmed. However, under many conditions, the necessity of prearranging the transmissions from the various stations is untenable rendering these systems practically useless in many cases. This is particularly true in the case of press conferences and auctions for example; or in the case of contests which require that talkers at each station be provided with the opportunity of speaking without prearrangement. Arrangements which require transmission to takeV place in a prearranged sequence, or which fail to provide continuous reception of the other stations while a given station is transmitting, are not capable of performing the functions of the present invention.

The conventional system generally employed for permitting simultaneous communicating among a plurality includes a master or control station which continuously receives signals from the other remotely :spaced subscriber stations by way of individual channels or lines connecting each of the respective subscriber stations to the master station. The various signals received by the master station are mixed with a locally generated signal and the total mixed signal transmitted by way of a common network channel to the various subscriber stations where the network signal is amplified and transduced in the usual manner. This system possesses some major drawbacks. In addition to the common network channel, an additional channel is required for each subscriber station connecting it to the master station. This is particularly undesirable and highly expensive when the subscriber stations are numerous and spaced great distances from the master station.

A further important drawback of the aforesaid system, particularly where great distances are involved, is the inferior performance thereof by reason of the presence of what is known in the art as an echo. It has been observed that when the stations are widely separated the round trip transmission time which elapses betwen the moment when a talker at a distant station speaks and when his voice is returned on the network overall channel is so great that the talker no longer perceives the return transduced signal from his loudspeaker as a form of side tone, but rather perceives it as a distinctly separate sound or echo. This eiect is further agice gravated when the talker is some distance fromthe loudspeaker (as in an auditorium audience situation), and a considerable sonic transmission interval is combined with the electrical transmission delay. When this delay approaches approximately 25 to 50 milli-seconds,.many individuals experience great diiiiculty in continuing to talk. This psychological effect is attributable to the fact that many individuals cannot distinguish the reproduced sound of their own audio signal from the reproduction of audio signals caused by talkers at other stations; and therefore, upon hearing the delayed reproduction of their initiai utterance, they often receive the impression that a distant talker is trying to interrupt them and stop talking to listen. Talkers who are not expecting this to occur can become severely confused, and even those who have a technical understanding of what is happening ind the ability to carry on a conversation severely impaired. This is a great disadvantage on programs where conference communications are desired andwhere it is desirable that talkers be able to interrupt each other or be aware that two talkers have spoken or are speaking at the same moment (as for example two bidders shouting at the same moment in an auction).

While there have been many attempts to eliminate or minimize the echo in multistation communication systems of the above type, the results have been of little practical success since they have resulted in systems which were highly complex and required closely attended switching operations.

it is therefore a principal object of the present invention to provide an improved communication system.

Another object of the present invention is to provide an improved system permitting simultaneous common communication among a plurality of remotely spaced stations.V

Still another object of the present invention is to provide an improved system permitting simultaneous common communication among a plurality of remotely spaced stations and characterized by the substantial absence of any echos.

A further object of the present invention is to provide an improved system permitting simultaneous common communication -among a plurality ofv remotely spaced stations without the necessity of any switching operations.

Still a further object of the present invention is to provide an improved communications system of the above nature wherein the number and lengths of interconnecting channels are greatly minimized.

Another object of the present invention is to provide a communications system of the above nature wherein additional stations may be readily and easily added.

Still another object of the present invention is to provide a communications system of the above nature characterized by its ruggedness, low cost, ease of operation and quality of performance.

The above and other objects of the present invention willbecome apparent from a reading ofthe following ydescription taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a schematic block diagram of a communications system embodying the present invention; and

FIGURE 2 is a schmatic circuit diagram of an intermediate station which may advantageously be employed iri the present improved communications system.

The multistation communications system of the present invention is characterized by the absence of any echo without the need of any switching arrangement, and with the employment of a minimum of communication channels, only a pair of incoming channels and a pair of outgoing channels at each intermediate station and only test room exchanges.

a pair of channels at the terminating stations. An important feature of the present communications system resides in the provision of a plurality of remotely separated stations, each including a local mixer network anda local vsignal generator. At each station the signals originating at the other stations are mixed with the locallygenerate'd signal by the local mixer network and the combined signals may then be transduced in the usual manner. Another important feature of the present system is the provision at each of the intermediate stations of 'mixer networks which receive a signal from a trailing station, mixes it with the lo'cally generated signal and transmits it to a leading station and receives a signal from a leading station, mixes it with the locally generated signal and transmits it to the trailing station. Thus, 'each intermediate station includes two incoming and two out-going channels. While in the system hereinafter described as a preferred form of the present invention, each of the channels is in the form of a pair of conductors which pass through corresponding test room exchanges, the channels may take any lknown form and may be carried on common lines. For example they may be transmitted as separate bands on a common cable, may be transmitted as modulated radio frequency carriers or the like.

The present invention in` one sense differs from former methods in that at no point inthe channels between stations or ytest room exchanges does any channel contain the-total yprogram-content. The content of any channel existing between test room exchanges is unique when compared to the content of other channels; however, if the content of any two channels existent between the same test room exchanges would -be combined the total program would result. The possibility of deriving the total program by the addition of any two channels existing between test room exchanges is` an improvement over former systems in that it permits the addition of other stations which are enabled to both transmit and receive, without -the vemployment of additional'channels between -A further advantage of transmitting the sum of the total program via two channels, with neither channel containing the complete signal, is that doing Yso makes possible the separation of the functions of mixing the program for the local audience from the function of mixing signals for en route transmission for the stations.

The fact that each en route stations own signals are immediately added to the bi-directional transmission of the lprogram en route, makes it possible to combine the overall program for-the local audience and for any local participants, from'sources that are free of any delayed echo return, since the local talkers voice is not obliged to travel many miles in order to be addedto the program. A Afurther advantage of the present system is that by monitoring of the eastbound and westbound (or equiva- Alents) signals at the terminus stations it is possible to detect any breaks in the transmission of signals-through the en route stations. There are certain types of programs such as auctions or contests where it is essential that allparticipants have an equal opportunity to participate in the program, and that in the event of a failure to any one of the stations, such failure be detected immediately and the program halted untilY transmission to all vparticipants is restored.' An advantage of the present system over the prior systems is that channel failures in the entire system (inclusive of channels between Ytest rooms. and stations as well-asbetween'the testrooms) -can be detected by merely monitoring Vthe incoming channel atterminus stations. v

Referring niow to `the drawings which illustrate a Apreferred embodiment of the 'present invention, the irnproved communications system includes a pair of terminal stationsW'and Eand one or more intermediate stations-CwhichY maybe of'identical construction. Associated with each of the stations in' the usual manner are test room exchanges WE, IE, and EE respectively,

each of the intermediate exchanges being connected to the next trailing exchange by a pair of east-bound and west-bound channels CE1 and CW1 and to the next 5 leading exchange by a pair of east-bound and westbound channels CEZ and CWZ. It should be noted that the terminal stations WE and EE are each provided Ywith only one pair of east-bound and west-bound channels and that the channels CE1 and CWl of one exchange corresponds to channels CE2 and CWZ of the next succeeding exchange and vice-versa.

Located at each of the intermediate stations C are first, second and third signal mixing networks 11, l2 and 13 which may be of any well lknown type and include audio amplifiers. Also disposed at the station C is a microphone or other signal generating transducer 14 ,which 'is connected -by way of a variable attenuator 16 to the input of an audio amplifier17. The output of the audio amplifier 17 is connected to the input of the mixer network 11 by way of a variable attenuator 18, to the mixer network 12 by way of a variable attenuator .19 and to the mixer network 13 by way of a variable Vattenuator 20. The channel CE1 is connected through the exchange "IE to the inputs of mixer networks 12 and 13 by way of variable attenuators 21 and 22 respectively vand `the channel CWZ is connected through the exchange IE to the mixer networks 11 and 13 by way of variable attenuators 22a and 23 respectively.

The output vof the mixer network l1 is connected through the exchange IE to channel CWll and the output of themixer network 12 is connected through the exchange IE to the channel CE2. The network 13 has associated therewith an audio power amplifier the output of which drives a loudspeaker 2o. The loudspeaker ,Z6 and the microphone 14 are acoustically isolated from each othery in any well known manner to prevent acoustic feed-back. For example the microphone 14 and speaker Zo'may be vof the directional types and suitably located and oriented.

Each of the terminal stations W and E likewise includes af loudspeaker' 28 and a microphone 29 which are acoustically isolated from each other. The loudspeaker 28 is connected to the outputof a power ampliier and signal mixing network 30 to the input of which .45 are connected the channels CE and CW by way of variable attenuators 32 and 33 respectively. In station W the microphone 29 is connected through a variable attenuator 34 and an amplifier 36 to the channel CE and in station E the microphone 29 is connected through a variable attenuator 34 andv an amplifier 36 to the channel CW.

In the operation of the improved communications system described above a signal generated at the terminal station W bythe microphone 29 is delivered at the desired level by way of thevariable attenuator 34 and amplifier 36 to the channel CE and to the mixer amplifier by way of the variable attenuator 32. Also delivered to the mixer amplifier 30 through variable attenuator 33 is the aggregate signal from the other stations by way of channel CW.

Thus the signal delivered to the loudspeaker is the sum of lfthe locally generated undelaye/l .signal land the signals originating at all the other stations. The terminal station W operatesin a like manner. Atveach of the intermediate stations C the-local mixer network 11 receives the aggregate of the signals generated at the leading stations eastwardly thereof by way of channel CWZ and mixes it'with the signal locally generated by the microphone 14 'and transmits these by way of channel CWI to the next succeeding trailing station. Similarly, the mixer network'lZ receives the aggregate of the signals generated at the trailing stations, westwardly thereof by way of the channel CE1 and mixes it with the locally generated signal and transmits these by way of channel CE2 to the next succeeding-leading station. Furthermore, the aggregate arenoso signals received from the leading and trailing stations by way of channels CW2 and CE1 are mixed with the locally generated signal by the network 13 and locally enunciated by speaker 26.

It is apparent from the above, as has been earlier set forth, that at each of the stations the signals from all of the stations are received, mixed locally with the locally generated signal and transduced. lnasmuch as there is no delay of the locally generated signal, no echo whatsoever is experienced. Moreover, the number of channels which connects any two stations is always only two in number and is independent of the number of stations. Furthermore, the `Signals appearing on any vof the channels between any pair of stations is different from the signals on any other channel. It is important to note that the signals in any pair of channels connecting successive stations contains the signals generated at all the stations, no signal appearing on both channels. As a consequence, an additional intermediate station may be simply hooked into any pair of channels, in the manner set forth above, without interfering with the operation of the overall system. The added intermediate station may or may not introduce another locally generated signal as desired. The various variable attenuators permit the adjustment of the signals to-their optimum levels.

In FIGURE 2 of the drawings there is illustrated a circuit network of an intermediate station which may be advantageously employed in the present system and includes the microphone 14 and loudspeaker 26 and has incoming channel cables CB1 and CWZ and outgoing channel cables CE2 and CWl. Each of the channels CE1 and CW2 are connected by way of a four pole double throw switch 40 to the input of a signal dividing attenuation pad 4l, the Y switch iii permitting the insertion of an attenuation pad 42 into the line where the lines are at a standard low level. The inlet terminals of the pad 42 are connected to one pair of the normally open switch contacts and the output terminals thereof to the other pair of the normally open switch contacts. Opposite normally closed switch contacts are interconnected and one pair of switch arms is connected to the incoming channel and the other pair is connected to the input of the pad 4l.. Thus, the incoming channel is normally connected directly to the pad 41 and is connected thereto by way of the pad 42 upon throwing of the switch 4d for high level line operation.

The pad 41 includes opposite pairs of series connected resistors R1, R2 and R3, the Ril-R2 junctions being bridged by a resistor R4 and the R3 termini being bridged by a resistor R5. The attenuated outputs of the pads 41 are taken from the opposite RZ-RS and RS-RS junctions are connected to the inputs of variable attenuators 43 and 44.

The microphone 14 is connected to the input of an amplifier 46 the output of which is connected by way of resistor H-pads 47, i8 and 49 to the inputs of variable attenuators S0, 51 and 52 respectively. The outputs of the variable attenautors 43 are connected to the inputs of respective transformers T1 by way of resistors R5 and R7 and the outputs of the variable attenuators Sti and 51 are connected to the inputs of transformers T1 by way of resistors RS and R7. The outputs of the variable attenuators 44 and 52 are connected through corresponding resistors R9 and a common resistor R19 to the input of a variable attenuator 53. The output of the attenuator 53 is connected by way of a transformer T2 to the input of a suitable audio amplier 54 the output of -which is connected to the loudspeaker 26.

The outputs ofthe transformers T1 are connected to the inputs of amplifiers 56 the outputs of which are connected through attenuating pads S7 to the outgoing channels CE2 and CW1 respectively. Also connected to the outputs of each of the amplifiers S5 is a v.u. meter network and a headset monitoring jack S9 by way of pairs of resistors R11.

The following are examples of the values of the various o l components which may be employed in the network above described: R1, R2-67 ohms; R3, R5-600 ohms; R4-

R11-2000 ohms. The attenuation at midpoint of variable attenuators 43, Si), 51 is 20 db, and that of variable attenuators 44, 52 and 53 is 10 db. The attenuation of attenuator pad 42 is l0 db, of pad 41 is l0 db, and of pad 57 is 6 db.

Under normal operating conditions the level of the signals entering the pad 41 is about 20 V.u. and entering the attenuators 43, 4d, 5o, 51 and 52 about -30 v.u. The output of amplier 46 is about 8 v.u. which is attenuated by H-pads 47, 43 and 49 to -30 v.u. The loss in resistors R6, R7 and R8 is about 6 db feeding a signal at about -56 v.u. to amplifiers 56 which ampliiies it to about 14 v.u., the signal then being attenuated by pads 57 to 8 v u. and fed to outgoing channels CE2 and CW1. The signal level at the input to attenuator S3 is about -50 v.u. and to transformer T2 about -60 v.u. It should be noted that the above values are given merely by way of example and may be adjusted and varied according to the operating conditions in any manner well known in the art.

The operation of the last described network in the present system is lapparent from the `ab ove and requires n-o further explanation.

While there has been described and illustrated a preferred embodiment of the present invention, it is obvious that numerous alterations, omissions and additions may be made without departing from the spirit'thereof.

What is claimed is:

1. A network for providing substantially simultaneous multidirectional communication among a plurality of remotely separated stations including a signal transmitting and receiving leading station, a signal transmitting and receiving trailing station and a signal receiving and transmitting intermediate station, a rst pair of incoming and outgoing channels connecting Said intermediate station with said trailing station and a second pair of incoming and outgoing channels connecting said intermediate station with said leading station, a local signal generator disposed at said intermediate station; a irst network at said intermediate station mixing the locally generated signal with the signal received from said rst incoming channel and transmitting the combined signals along said second outgoing channel, a second network at said intermediate station mixing said signal received from said second incoming channel with said locally generated signal and transmitting the combined signals along said rst otitgoing channel, a third network located at said intermediate station mixing said locally generated signal with said signals from said rst and second incoming channels, and an electroaudio transducer connected to the output of said third mixer network.

2. A communications network in accordance with claim 1, including a iirst signal dividing network connected between said frst incoming channel and said first and third mixer networks and a second signal dividing network connected between said second incoming channel and said second and third mixer networks.

3. A communications network in accordance with claim 1 including iirst variable attenuators connected between each of said incoming channels and said rst and second mixer networks, respectively, second variable attenuators connected between said signal generator and said rst and second mixer networks respectively and third variable attenuators connected between said third mixer network and said irst and second incoming channels and said generator respectively.

4. A network for providing substantially simultaneous multidirectional communication among a plurality of remotely separated stations including an intermediate station, a trailing station and a leading station, comprising rst and second communication means connecting said intermediate station and said trailing station and third and fourth communication means connecting said intermixer network having an input coupled to said irst communication means and said signal generating device and an output coupled to said third communication means, a second mixer network located at said intermediate-station and having an input coupled to said Signal generating device and said fourth communication means and an output coupled to said second communication means, and a third mixer network located at said intermediate station and having an input coupled to said signal generating device and said iirst and fourth communication means.

5. A communications network in accordance with claim 4 including an electroaudio transducer connected tothe output of said third mixer network.

6. A communications network in accordance with claim 4 wherein said signal generating device includes a microphone.

7. A communications network in accordance with claim 6 including a loudspeaker connected .tothe output of said third mixer network, said microphone and said loudspeaker being substantially acoustically `isolated fro'meach other. f

S. A communications network including a lsignal transmitting and receiving leading station, a signal transmitting and receiving trailing station and a signaland transmitting intermediate station, arst pair of incoming and outgoing channels connecting said intermediate station with said 4trailing station and a second pair of incoming and outgoing channels connecting said intermediate ,station with said leading station, a local signal generator disposed at said intermediate station, a irst network at 4said intermediate station mixing the locally generated signal with the'si'gnal received from said first incoming channel and transmitting the combined signals along said 'second outgoing channel, a'. second network ,at said intermediate station mixing said signal received from said sec- .ond incoming channel with said locally lgenerated. signal and transmitting the combined signals along said iir'st outgoing channel, iirst variable lattenuators connected be tween each of saidV incomingchannels `and said ii'r'st and second mixer .networks respectively, and second variable attenuators ,connected between said signal `generator and said iirst and second mixer networks respectively.

References `Cited by the Examiner UNITED STATES PATENTS 2,296,626 9/42 Blumiein 179-1 2,395,540 2/46 Edwards 179--170 2,427,496 9/47 Feldscher 179-1 2,515,726 7/570 Montani 179-1 2,759.999 8/56 Foster et al. 179-1 2,871,291 1/59 Horner 179-1 3,054,859 9/62 Brown 179-170 ROBERT H. ROSE, Primary Examiner.

L. MILLER ANDRUS, THOMAS B. HABECKER,

Examiners; 

1. A NETWORK FOR PROVIDING SUBSTANTIALLY SIMULTANEOUS MULTIDIRECTIONAL COMMUNICATION AMONG A PLURALITY OF REMOTELY SEPARATED STATIONS INCLUDING A SIGNAL TRANSMITTING AND AND RECEIVING LEADING STATION, A SIGNAL TRANSMTTING AND RECEIVING TRAILING STATION AND A SIGNAL RECEIVING AND TRANSMITTING INTERMEDIATE STATION, A FIRST PAIR OF INCOMING AND OUTGOING CHANNELS CONNECTING SAID INTERMEDIATE STATION WITH SAID TRAILING STATION AND A SECOND PAIR OF INCOMING AND OUTGOING CHANNELS CONNECTING SAID INTERMEDIATE STATION WITH SAID LEADING STATION, A LOCAL SIGNAL GENERATOR DISPOSED AT SAID INTERMEDIATE STATION; A FIRST NETWORK AT SAID INTERMEDIATE STATION MIXING THE LOCALLY GENERATED SIGNAL WITH THE SIGNAL RECEIVED FROM SAID FIRST INCOMING CHANNEL AND TRANSMITTING THE COMBINED SIGNALS ALONG SAID SECOND OUTGOING CHANNEL, A SECOND NETWORK AT SAID INTERMEDIATE STATION MIXING SAID SIGNAL RECEIVED FROM SAID SECOND INCOMING CHANNEL WITH SAID LOCALLY GENERATED SIGNAL AND TRANSMITTING THE COMBINED SIGNALS ALONG SAID FIRST OURGING CHANNEL, A THIRD NETWORK LOCATED AT SAID INTERMEDIATE STATION MIXING SAID LOCALLY GENERATED SIGNAL WITH SAID SIGNALS FROM SAID FIRST AND SECOND INCOMING CHANNELS, AND AN ELECTROAUDIO TRANSDUCER CONNECTED TO THE OUTPUT OF SAID THIRD MIXER NETWORK. 